Injection stretch blow molding method with upright preform molding and inverted blow molding

ABSTRACT

In an injection stretch blow molding method, at least one injection molded preform is transferred from a preform molding section to a blow molding section by way of a transfer section and the at least one preform is blow molded into at least one container in the blow molding section. In the preform molding section the at least one preform is injection molded in an upright state with an open neck section thereof facing upward. In the transfer section, the at least one upright preform is turned upside-down and transferred to the blow molding section in an inverted state. Then, the blow molding section blow molds at least one container from the at least one inverted preform.

This divisional application is continuing application of U.S. patentapplication Ser. No. 08/474,746 filed Jun. 7, 1995 now U.S. Pat. No.5,744,176 and is related to Ser. No. 08/528,193 filed Sep. 14, 1995 nowU.S. Pat. No. 5,753,279, both incorporated by reference herein.

BACKGROUND OF THE INVENTION

This invention relates to an injection stretch blow molding apparatusand method wherein containers are stretch blow molded from preformsretaining heat from when they were injection molded. This invention alsorelates to an injection stretch blow molding apparatus and methodwherein N (N≧2) preforms are simultaneously injection molded and n(1≦n<N) preforms among these are simultaneously blow molded into ncontainers. More particularly, the invention relates to an injectionstretch blow molding apparatus and method with which while ample coolingtime is provided the preforms can be molded with a shortened injectionmolding cycle time and furthermore the operation rate of the blowcavities can be increased. Also, this invention relates to constructionsand methods for heating and adjusting the temperature of the preformsbefore they are blow molded. Also, this invention relates to aninjection stretch blow molding apparatus and method with which it ispossible when necessary to discharge the preforms to outside theapparatus instead of carrying them to the blow molding section.

Methods for blow molding a container from a preform (parison) includethat known as the cold parison or 2-stage method and that which is knownas the hot parison or 1-stage method. In both these methods, forinjection molding the preforms required for the blow molding, at leastan injection cavity mold which shapes the outer wall of the preform andan injection core mold which shapes the inner wall of the preform arenecessary. Also, after the injection cavity mold and the injection coremold are clamped together and the preform is injection molded, with themolds still clamped together it is necessary to cool the preform down toa temperature at which the preform can be released from the molds.

Particularly in the case of the cold parison (2-stage) method, becausethis preform mold-release temperature has to be made quite low, theinjection molding cycle time has been long and productivity has beenpoor. This is because when the preform is ejected by the injectioncavity mold and the injection core mold being released from the preformand the preform being dropped or the like, it is necessary for thepreform to be cooled to a mold-release temperature low enough for thepreform not to be deformed when it makes contact with other members.

In the case of the cold parison method, because the preform molding stepand the step in which a container is blow molded from this preform arecompletely release, the blow molding cycle time is not affected by theinjection molding cycle time. However, because the cold parison methodinvolves reheating preforms which have been cooled to room temperaturethe cold parison method is inferior to the hot parison method in itsenergy efficiency.

In a hot parison (1-stage) method injection stretch blow molding machinewhich draw blow molds bottles from preforms still containing heat fromwhen they were injection molded the cycle time of the overall apparatusis determined by the injection molding cycle time, which of all thecycles is the one requiring the most time. Consequently there has beenthe problem that when the time required for injection molding is long,the throughput of the whole apparatus is low.

In the case of the hot parison method, although the preform ismold-released at a higher temperature than in the cold parison method,there is a limit on this mold-release temperature and consequently it isnot possible to greatly speed up the injection molding cycle. One reasonfor this is that when the preform mold-release temperature is high, whenthe injection core mold is released from the preform, a mold-releasecalled lifting, wherein the preform sticks to the core mold, occurs.Also, after the injection core mold is released from the preform,because there is no longer any member restricting deformation of thepreform, deformation caused by temperature nonuniformity and thermalcontraction and the like make it impossible for preforms conforming tothe design to be ejected. Furthermore, when the cooling effected by theinjection core mold is inadequate, crystallization caused by inadequatecooling occurs, particularly at the inner wall of the preform, and apreform of which the trunk portion is opaque is ejected.

Also, when preforms are ejected before they are completely cooled by theinjection core mold and the injection cavity mold (with the preformsstill at a temperature at which blow molding is possible) and blowmolding is carried out thereafter, there have been the followingproblems:

(A) Unless the internal pressure (injection sustain pressure) is raised,shrink marks form at the injection cavity mold side of the preform and apreform with a uniform temperature distribution cannot be obtained.Consequently, when this preform is blow molded, a molded product with auniform wall thickness distribution cannot be obtained.

(B) When the internal pressure (injection sustain pressure) is raised, apressure differential forms between the gate portion and the preform endportion (for example the neck portion), and the resulting preform haslarge residual stresses at the preform bottom end where the pressure washigh. Consequently, when the preform is blow molded, a molded productwith a uniform wall thickness distribution cannot be obtained.

(C) When the preform is cooled by the injection core mold and theinjection cavity mold, as the cooling progresses the preform contractsand tends to move away from the injection cavity surface. Because ofthis, there are some parts of the outer wall surface of the preformwhich are in contact with the injection cavity and some parts which arenot in contact with the injection cavity, and consequently differentparts of the preform cool at different rates and the temperature becomesuneven. As a result, when this preform is blow molded, a molded productof uniform wall thickness cannot be obtained.

Thus, in a conventional hot parison system, unless the preform is amplycooled by the injection cavity mold and the injection core mold it hasnot been possible to obtain good blowing characteristics or good bottlecharacteristics. Because of this, the injection molding of the preformshas required time, and the throughput of the apparatus has been low.

Various other problems have also been associated with injection stretchblow molding machines using the hot parison method, including thefollowing:

When in order to increase the throughput the number N of preformsinjection molded simultaneously is increased, the same number N ofcavities conforming to the external shape of the bottles beingmanufactured have to be formed in the blow cavity mold. Of the moldsused in a blow molding machine the blow cavity mold is the mostexpensive, and the cost of this blow cavity mold increases roughly inproportion to the number of cavities in it. Even if a mold is expensive,if its operation rate is high then it can be used cost-effectively;however, because as described above the cycle time of the overallapparatus depends on the injection molding cycle time and cannot beshortened, the operation rate of each cavity in the blow cavity mold hasunavoidably been low. Also, when the number of bottles blow moldedsimultaneously increases, not only the number of cavities in the blowmold but also the number of drawing rods and blow core molds andmechanisms for supporting and driving these increases, and this hasresulted in increases in the size and cost of the apparatus.

Another problem has been that conventionally it has not been possible toeject the preforms unless the injection core mold is completely pulledout of the preforms, and consequently with a rotary injection moldingapparatus it has not been possible to carry the preforms from theinjection molding section to the next stage. When on the other hand theinjection core mold is completely pulled out of the preforms, there hasbeen the problem that this pullout stroke is long and the overall heightof the apparatus is high.

Another problem has been that when hot parison blow molding is carriedout by a rotary carrier type blow molding machine the injection moldedpreforms are always carried by the rotary carrier to the blow moldingsection. Here, for example when a problem has arisen in the blow moldingsection, there has been no alternative but to shut down the preforminjection molding as well as the blow molding section. However, once theinjection molding section is shut down, a long starting-up time isrequired when it is restarted. This is because the injection apparatuscontains numerous resin-heating mechanisms in the hot runner mold andelsewhere.

As a result, as well as it not being possible to raise the throughput ofthe overall apparatus, as described above, a lot of time is required forstarting up the apparatus when a problem has arisen, and theproductivity falls even further.

Accordingly, it is an object of the invention to provide an injectionstretch blow molding apparatus and method with which while ample preformcooling time is provided the injection molding cycle time can beshortened and the cycle time of the overall apparatus can thereby beshortened.

Another object of the invention is to provide a highly efficientinjection stretch blow molding apparatus and method with which whilereducing costs by reducing the number of cavities in the blow mold theoperation rate of the blow mold can be increased.

Another object of the invention is to provide an injection stretch blowmolding apparatus and method which while exploiting the heat energyefficiency of hot parison molding also has the preform temperaturedistribution stability of the cold parison method.

Another object of the invention is to provide an injection stretch blowmolding apparatus and method with which temperature nonuniformity anddeformation can be prevented even when the preform mold-releasetemperature at which the preforms are released from the injection cavitymold is made high and furthermore the preforms can be amply cooledbefore they are released from the injection core mold and can be stablyblow molded thereafter at a suitable blow molding temperature.

A further object of the invention is to provide an injection stretchblow molding apparatus and method with which the temperature differencebetween the inner and outer walls of the preforms is moderated beforethe preforms are blow molded.

A further object of the invention is to provide an injection stretchblow molding apparatus with which general-purpose medium-sizedcontainers of capacity 1 to 3 liters can be blow molded with highefficiency.

A further object of the invention is to provide a blow molding apparatuswith which it is possible to efficiently heat the regions below thenecks of the preforms to a suitable blow molding temperature.

A further object of the invention is to provide a blow molding apparatuswith which it is possible to moderate the temperature difference betweenthe inner and outer walls of the preforms and also use this timeprovided for temperature moderation to adjust the temperature of thepreforms to a suitable blow molding temperature before blow molding iscarried out.

A further object of the invention is to provide an injection stretchblow molding apparatus and method which can be started up without anywasteful blow molding being carried out at the time of start-up and withwhich it is not necessary to stop the operation of the whole apparatuswhen there is a problem in the blow molding section.

An injection stretch blow molding apparatus according to the inventioncomprises:

a preform molding station for injection molding preforms;

a blow molding station for stretch blow molding the preforms intocontainers; and

a transfer station for transferring the preforms from the preformmolding station to the blow molding station, wherein the preform moldingstation comprises:

a circulatory carrier for intermittently circulatorily carrying along acarrying path a plurality of injection core molds disposed apart;

an injection molding section for injection molding the preforms havingan injection cavity mold together with which the injection core molds,stopped in the carrying path, are severally clamped; and

an ejecting section for ejecting preforms from the injection core moldsby releasing the injection core molds, stopped in the carrying path, andthe preforms.

An injection stretch blow molding method according to the invention forblow molding containers from preforms retaining heat from when thepreforms were injection molded comprises the steps of:

releasing the preforms, molded using at least an injection core mold andan injection cavity mold, from the injection cavity mold;

with the preforms held by the injection core mold, carrying theinjection core mold to an ejecting section along a carrying path whilethe preforms are cooled by the injection core mold;

in the ejecting section, ejecting the preforms by releasing theinjection core mold therefrom; and

thereafter, blow molding the containers from the preforms retaining heatfrom when the preforms were injection molded.

According to these inventions, the preforms injection molded in theinjection molding section are cooled by the injection cavity mold andthe injection core mold and then the injection cavity mold only isreleased from the preforms. After that, the preforms are carried to thepreform ejecting section by the injection core mold. The preforms areejected after being cooled by the injection core mold during thiscarrying and in the preform ejecting section. As a result, by thepreforms being cooled by the injection core mold even after theinjection cavity mold is mold-released in the injection molding section,ample preform cooling time is provided. Therefore, the preformmold-release temperature at which the preforms are released from theinjection cavity mold can be made high, the injection molding cycle timecan thereby be shortened and the cycle time of the overall apparatus canbe shortened. Also, even when the preforms are released from theinjection cavity mold at a high temperature, deformation of the preformsis prevented by the injection core mold. Furthermore, not only does thecooling efficiency increase because the preforms contract into contactwith the injection core mold as they are cooled, and consequentlycrystallization and loss of transparency of the trunk portions of thepreforms caused by inadequate cooling is prevented, but also by thusstabilizing the cooling process it is possible to stabilize the amountof heat retained by the preforms and thereby stabilize the wallthickness distributions of successively blow molded containers.

According to another aspect of the invention, an injection stretch blowmolding apparatus comprises:

a preform molding station for injection molding preforms;

a blow molding station for stretch blow molding the preforms intocontainers; and

a transfer station for transferring the preforms from the preformmolding station to the blow molding station,

wherein the preform molding station comprises:

a first circulatory carrier for intermittently circulatorily carryingalong a first carrying path an injection core mold having N(N≧2) of corepins disposed apart;

an injection molding section for simultaneously injection molding N ofthe preforms, said injection molding section having an injection cavitymold including N of cavities in which the injection cavity mold isclamped together with the injection core mold stopped in the firstcarrying path; and

an ejecting section for ejecting preforms from the injection core moldby releasing from the injection core mold, stopped in the first carryingpath,

and the blow molding station comprises:

a second circulatory carrier for intermittently circulatorily carryingalong a second carrying path the preforms transferred from the preformmolding station by the transfer station; and

a blow molding section for simultaneously blow molding n (1≦n<N) ofcontainers from n of the preforms, said blow molding section having ablow mold including n of blow cavities in which the blow mold is clampedaround the preforms stopped in the second carrying path.

According to another aspect of the invention, an injection stretch blowmolding method for molding containers from preforms retaining heat fromwhen the preforms were injection molded, comprising the steps of:

releasing N (N≧2) of the preforms, molded using at least an injectioncore mold and an injection cavity mold, from the injection cavity mold;

with the preforms held by the injection core mold, carrying theinjection core mold to an ejecting section along a first circulatorycarrying path while the preforms are cooled by the injection core mold;

in the ejecting section, ejecting the preforms by releasing from theinjection core mold;

transferring the ejected preforms to carrier members to be carried alonga second circulatory carrying path;

carrying the carrier members supporting the preforms along the secondcarrying path to a blow molding section; and

in the blow molding section, simultaneously blow molding n (1≦n<N) ofcontainers from n of the preforms in a blow mold clamped around n of thepreforms.

According to these inventions, the inventions provide the followingoperations and effects in addition to those of the inventions asdescribed above: Because the number n of preforms simultaneously blowmolded is made smaller than the number N of preforms simultaneouslyinjection molded, fewer cavities are required in the blow mold and moldcosts, molds being consumable items, can be greatly reduced. Also,because fewer blow core molds, stretching rods, and mechanisms forsupporting and driving these are required, the apparatus can be mademore compact and cheaper. Furthermore, because N simultaneously moldedpreforms are blow molded n (n≦N) at a time over a plurality of blowmolding cycles within the shortened injection molding cycle time, theoperating rate of the n cavities in the blow cavity mold increases.

Here, a heating section for heating the preforms being carried to theblow molding section can be provided. When this is done, the preformscan be brought to a temperature suitable for blow molding by coolingperformed by the injection molds and reheating of the cooled preforms,and the temperature stability from cycle to cycle therefore increases.Also, even though N simultaneously injection molded preforms are blowmolded n preforms at a time over (N/n) blow molding cycles, controlreducing the temperature variation among blow molding cycles can easilybe carried out.

Also, when the preforms being heated are rotated about their verticalcenter axes, heating unevenness is reduced and temperature nonuniformityin the circumferential direction of the preforms can thereby be reduced.

Furthermore, a second circulatory carrier comprises a plurality ofcarrier members which remain spaced at equal intervals along the secondcarrying path, and each of the carrier members has a supporting portionfor supporting a preform in an inverted or an upright state. It ispreferable that the array pitch at which the plurality of carriermembers are spaced along the second carrier path be made equal to thearray pitch P of the plurality of cavities in the blow cavity mold. Thisis because it makes pitch conversion in the carrying processunnecessary. When this is done, the array pitch of the preforms in theheating section of the invention is greater than the small pitch atwhich the preforms are arrayed in the heating section in a conventional2-stage system. However, because in this invention it is only necessaryto give the preforms a small amount of heat energy in addition to theheat which they retain from when they were injection molded, the heatingtime can be short and the length of the heating section does not have tobe made long as it does in the cold parison case.

Also, in the method of this invention, a step of allowing the preformsto cool between the separation of the preforms from the injection coremold and the start of the blow molding step, over a period of time longenough for the temperature difference between the inner and outer wallsof the preforms to be moderated, can be provided. Here, when the methodof this invention is applied, because the period of time for which thepreforms are cooled by the injection core mold in contact with theirinner walls is made longer than conventionally, a relatively steeptemperature gradient forms between the inner and outer walls of thepreforms, and the temperature in the outer wall vicinity becomes greaterthan that in the inner wall vicinity. By providing this cooling step,this temperature gradient can be moderated and the inner and outer wallsof the preforms can be brought to a temperature suitable for blowmolding.

Also, in the method of this invention, it is preferable that in the blowmolding step n (n≧2) containers simultaneously be blow molded from npreforms using n blow cavities arrayed at a blow molding pitch P, thatthe preforms being carried along the second carrying path be carriedwith the array pitch of the carrier members kept equal to this pitch P,and that in the preform transferring step a process wherein n preformsare simultaneously transferred to n carrier members is repeated aplurality of times.

When this is done, as well as no carrying pitch conversion in the secondcarrying path being necessary, even if the number of preformssimultaneously injection molded N is increased, because only n preformsare transferred at a time, fewer than when N preforms are simultaneouslytransferred, the preforms can be easily correctly positioned on thecarrier members, and also no complex mechanisms are required to do this.

According to another aspect of the invention, an injection stretch blowmolding method wherein injection molded preforms are transferred from apreform molding station to a blow molding station by way of a transferstation and the preforms are blow molded into containers in the blowmolding station is characterized in that:

in the preform molding station the preforms are injection molded in anupright state with open neck portions thereof facing upward;

the transfer station turns the upright preforms upside-down andtransfers the preforms to the blow molding station in an inverted state;and

the blow molding station blow molds containers from the invertedpreforms.

According to the invention, the preforms are molded in an upright statewith their neck portions facing upward. As a result, the injection moldclamping is vertical clamping and is therefore space-saving. Also,because resin is normally injected from the preform bottom portion side,a stable arrangement wherein the injecting apparatus and the injectioncavity mold are disposed on a machine bed and the injection core mold isdisposed thereabove can be employed. Also, because when the preforms arecarried to the blow molding station they are in an inverted state, theopenings at their neck portions can be used to have the preforms supportthemselves easily. Furthermore, because the drawing rods and blow coremolds consequently have to be positioned underneath the preforms, theycan be disposed using a space in the machine bed and the overall heightof the blow molding section can be made low.

According to another aspect of the invention, an injection stretch blowmolding method comprises the steps of:

simultaneously injection molding N of preforms made of polyethyleneterephthalate using at least an injection core mold and an injectioncavity mold;

releasing the preforms from the injection cavity mold;

carrying the preforms to an ejecting section while cooling the preformsby means of the injection core mold;

in the ejecting section, after the preforms have been cooled to apredetermined temperature, ejecting the preforms from the injection coremold;

heating the ejected preforms to a predetermined temperature; and

thereafter, simultaneously blow molding n of containers from n of thepreforms,

wherein the ratio of the numbers N and n is N:n=3:1.

According to experiments carried out by the present inventors, in thecase of a general-purpose medium-sized container of capacity 1 to 3liters having a relatively small mouth (the diameter of the opening inthe neck portion 2 being about 28 to 38 mm) for which the market demandis large, the ratio of the simultaneous molding numbers N, n shouldideally be set to N:n=3:1. That is, it has been found that in the caseof this invention wherein the preforms continue to be cooled by theinjection core mold even after the preforms are removed from theinjection cavity mold and then blow molded thereafter, the time requiredfor the injection molding of a preform for a general-purposemedium-sized container is shortened to approximately 3/4 of that in thecase of a conventional injection stretch blow molding apparatus, and aninjection molding cycle time of approximately 10 to 15 seconds issufficient. A blow molding cycle time, on the other hand, of 3.6 to 4.0seconds is sufficient. Therefore, if this injection molding cycle timeis T1 and the blow molding cycle time is T2, the ratio T1:T2 is roughly3:1, and to mold general-purpose medium-sized containers efficiently thesimultaneous molding numbers N, n should ideally be set according tothis ratio.

According to another aspect of the invention, an injection stretch blowmolding method comprises the steps of:

simultaneously injection molding N (N≧2) of preforms; and

simultaneously blow molding n (1≦n<N) of containers from n of thepreforms retaining heat from when the preforms were injection molded,

wherein N/n is an integer when the injection and blow molding steps arerepeated.

When N/n is an integer, for example the N preforms simultaneouslyinjection molded in a first cycle are all used over an integral number(N/n) of blow molding cycles n at a time, and none of these preforms aremixed with and simultaneously blow molded with any of the N preformssimultaneously molded in the subsequent second cycle. If preforms fromdifferent injection molding cycles are mixed and blow molded together,the carrying sequence is different from the case wherein preforms moldedin the same injection molding cycle are simultaneously blow moldedtogether, and the control and structure of the apparatus becomecomplicated; however, this invention eliminates this problem.

According to another aspect of the invention, a blow molding apparatuswherein preforms carried in an inverted state with neck portions thereoffacing downward or in an upright state with the neck portions facingupward are heated in a heating section before being carried to a blowmolding section is characterized in that:

the heating section comprises:

a plurality of first heaters disposed at one side of a preform carryingpath, spaced apart in a vertical direction and extending in a preformcarrying direction;

a reflecting plate disposed facing the first heaters across the preformcarrying path; and

a plurality of second heaters extending in the preform carryingdirection on both sides of the preform carrying path,

wherein the second heaters are positioned at such a height in thevertical direction that they face regions subject to blow molding in thevicinities of the neck portions of the preforms.

According to the invention, although the region below the neck portionwhen the preform is upright is the nearest to the cavity surface of theblow cavity mold, it is a region which is to be draw orientatedrelatively much. By heating this region with the second heaters oneither side of the preform, it can be heated to a higher temperaturethan the trunk portion region heated by the first heaters disposed onone side only, and a high drawing orientation degree can be secured.Also, because the first heaters are disposed on one side only, thearrangement is saving. Furthermore, because the efficiency with whichthe region below the neck is heated increases, there is the benefit thatthe heating time can be shortened and the overall length of the heatingsection can be made short.

According to another aspect of the invention, a blow molding apparatuscomprises:

carrier members which support and intermittently circulatorily carrypreforms;

a heating section having heaters extending in a preform carryingdirection;

an endless carrying member running along the preform carrying directionat least through a heating zone of the heating section; and

a driver for driving the endless carrying member in a forward direction,

wherein each of the carrier members has a rotary driven member formeshing with the endless carrying member and a preform supportingportion which rotates integrally with the rotary driven member, and

the forward direction of the endless carrying member where it mesheswith the rotary driven members is opposite to the preform carryingdirection.

According to the invention, while the preforms are stopped the preformsare rotated in one direction by the meshing of the endless carryingmember moving forward in a fixed direction and the rotary driven memberrotated in a fixed position, and temperature nonuniformity of thepreforms can thereby be prevented. Also, when the preforms are moving,because the endless carrying member moves forward in the oppositedirection to that in which the preforms are being carried, the preformsare rotated faster in the same direction and temperature nonuniformityis similarly prevented. If the endless carrying member were to moveforward along with the preforms in the same direction as the rotarydriven member, because the preforms would only be rotated by the speeddifferential between the endless carrying member and the rotary drivenmember, the preforms would rotate slowly or not at all. Also, therewould be cases wherein the direction of the rotation of the preforms wasdifferent from that as of when the preforms were stopped. All thesesituations would cause temperature nonuniformity in the preforms;however, according to the invention, this temperature nonuniformity iseliminated.

According to another aspect of the invention, a blow molding apparatuswherein preforms are intermittently carried to a blow molding sectionvia a heating section is characterized in that:

the heating section comprises a heater extending in a preform carryingdirection at one side of a preform carrying path, and

in the carrying path between the heating section and the blow moldingsection a standby section is provided where at least enough number ofpreforms for one blow molding cycle are stopped and made to standbybefore being carried into the blow molding section.

According to the invention, by a standby section being provided beforethe blow molding section, the temperature distributions in the syntheticresin preforms, which have poor thermal conductivity, can be moderated.Normally, because heating in the heating section is carried out fromaround the preforms, the inner wall temperature of the preforms becomeslower than the outer wall temperature. By having at least the number ofpreforms simultaneously blow molded standby after being heated in orderto moderate the resulting temperature gradients therein, the blowmolding characteristics are stabilized.

Also, by actively carrying out temperature adjustment on the preformsduring this temperature moderation time in the standby section, thepreforms can be given a temperature distribution for blow molding whichcould not be obtained just by simply heating the preforms while rotatingthem.

According to another aspect of the invention, an injection stretch blowmolding apparatus comprising a preform molding section for moldingpreforms and a blow molding section for blow molding containers from thepreforms retaining heat from when the preforms were injection molded ischaracterized in that:

at a location in a path along which the preforms are carried from thepreform molding section to the blow molding section there is provided adischarge guide section for guiding preforms which are not to be carriedto the blow molding section off the carrying path.

According to another aspect of the invention, an injection stretch blowmolding method wherein preforms are injection molded in a preformmolding section and these preforms are carried to a blow molding sectionand containers are blow molded from the preforms retaining heat fromwhen the preforms were injection molded comprises the steps of:

switching to either a container molding operating mode or a preformmolding operating mode; and

when the preform molding operating mode is switched to, part way alongthe preform carrying path leading to the blow molding section,discharging the preforms being molded in the preform molding section tooff the carrying path.

According to these inventions, because it is possible to dischargeimperfect preforms molded during molding start-up instead of carryingthem to the blow molding section, wasteful blow molding can be avoided.Also, when a problem arises in the blow molding section or whenadjustments have to be made thereto, repair or adjustment of the blowmolding section is possible without stopping the operation of thepreform molding station. Once the preform molding station is shut down,it takes a long time to restore the various heating mechanisms to astate wherein molding is possible; however, with this invention thiskind of wasteful starting up time is eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a preferred embodiment of the invention;

FIG. 2 is a front view of the preferred embodiment apparatus shown inFIG. 1;

FIG. 3 is a left side view of the preferred embodiment apparatus shownin FIG. 1;

FIG. 4 is an enlarged view of the main parts of the apparatus shown inFIG. 1;

FIG. 5 is an underside view of a rotary disc;

FIG. 6 is a perspective view showing the mold-released state of aninjection core mold when a neck presser plate has been lowered;

FIG. 7 is a partially sectional view showing the injection core mold anda neck cavity mold mounted on the rotary disc;

FIG. 8 is a view illustrating a preform ejecting drive mechanism;

FIG. 9 is an enlarged sectional view of portion A in FIG. 8;

FIG. 10 is a partially sectional view illustrating the mold-releasedstate of the injection core mold;

FIG. 11 is a partially sectional view illustrating a preform 1 ejectingoperation;

FIG. 12 is a view illustrating the operation of a transfer stationreceiving a preform;

FIG. 13 is a view illustrating the operation of a transfer stationhanding a preform over to a blow molding station;

FIG. 14 is a plan view of the transfer station;

FIG. 15 is a side view of the transfer station;

FIG. 16 is a plan view of a carrier member of a second circulatorycarrier provided in the blow molding station;

FIG. 17 is a side view of the carrier member shown in FIG. 16;

FIG. 18 is a partially cut-away front view of the carrier member shownin FIG. 16;

FIG. 19 is a side view in the preform carrying direction of a heatingsection;

FIG. 20 is a plan view showing in outline a rotating carrier mechanismof the heating section;

FIG. 21 is a plan view showing another preferred embodiment apparatus ofthe invention wherein the numbers of preforms molded simultaneously aredifferent from those of the apparatus of FIG. 1;

FIG. 22 is a view illustrating the operation of a transfer stationtransferring preforms while converting their pitch;

FIG. 23 is a sectional view of a temperature adjusting core disposed ina standby section;

FIG. 24 is a sectional view of a temperature adjusting pot disposed inthe standby section;

FIG. 25 is a sectional view of local temperature adjusting membersdisposed in the standby section; and

FIG. 26 is a view of a flat container blow molded after the temperatureadjusting shown in FIG. 25.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment wherein the method and apparatus of the inventionare applied will be described below with reference to the accompanyingdrawings.

Overall Constitution of the Apparatus

FIG. 1, FIG. 2 and FIG. 3 respectively are a plan view, a front view anda left side view of the apparatus of this preferred embodiment, and FIG.4 is an enlarged view showing the main parts of the apparatus of thepreferred embodiment. As shown in the drawings, the apparatus comprisesa preform molding station 10, a transfer station 200 and a blow moldingstation 300 disposed on a machine bed 8.

As shown in FIG. 2, the preform molding station 10 has a rotary disc 30which has an injection core mold 50 in each of two locations an angle ofrotation 180° apart and is a first circulatory carrier whichcirculatorily carries the injection core molds 50 intermittently along arotary carrying path. An injection molding section 14 facing aninjecting apparatus 12 and a preform ejecting section 16 facing thisinjection molding section 14 are respectively provided at the stoppingpositions of the injection core molds 50. The injection molding section14 has an injection cavity mold 42 to which an injection core mold 50can be clamped, and with this injection cavity mold 42 the injectionmolding section 14 simultaneously injection molds N (N≧2), for exampleN=4, preforms 1 at a time. In the preform ejecting section 16, theinjection core mold 50 is released from the preforms 1. In thispreferred embodiment, a neck portion of each preform 1 is molded bymeans of a neck cavity mold 60 which will be further discussed later,and the preforms 1 are held by this neck cavity mold 60 and theinjection core mold 50 and carried by the rotary disc 30 to the preformejecting section 16. In the preform ejecting section 16 the preforms 1are ejected by being released from the neck cavity mold 60 after apartial release of the injection core mold 50.

As shown in FIG. 1, the blow molding station 300 has a secondcirculatory carrier 302 comprising four sprockets 320a to 320d and acarrier chain 322 running around these sprockets. A plurality of forexample ten carrier members 330 are fixed to this carrier chain 322uniformly spaced apart, and a preform 1 or a bottle 6 is supported byeach carrier member 330. In the carrying path of the carrier members 330are provided a preform receiving section 304 which receives the preforms1 from the transfer station 200, a heating section 306 which heats thepreforms 1, a standby section 308 which causes the heated preforms 1 totemporarily standby, a blow molding section 310 which blow molds thepreforms 1 into bottles 6, and a bottle ejecting section 312 whichejects the bottles 6 to outside the apparatus.

The blow molding section 310 has a blow mold 378 which is clamped aroundthe preforms 1 and blow molds one bottle 6 from each of n (1≦n<N)preforms 1, for example n=1 preform 1.

The transfer station 200 transfers the preforms 1 ejected from thepreform ejecting section 16 of the preform molding station 10 to thepreform receiving section 304 of the blow molding station 300. In thepreform ejecting section 16 of the preform molding station 10 N preforms1, i.e. the number of preforms 1 simultaneously molded in the injectionmolding section 14, are ejected at a time, but in the transfer station200 n preforms 1, i.e. the number of preforms 1 simultaneously molded inthe blow molding section 310 of the blow molding station 300, aretransferred at a time. In the apparatus of this preferred embodiment,four preforms 1 simultaneously ejected by the preform ejecting section16 are transferred one at a time to the preform receiving section 304.Also, whereas in the preform molding station 10 the preforms 1 areinjection molded in an upright state, in the transfer station 200 thepreforms 1 are turned upside-down and transferred to the blow moldingstation 300 in an inverted state.

Preform Molding Station 10

First the preform molding station 10 will be described, with referenceto FIG. 1 to FIG. 11.

Injection Molding Section 14 and First Circulatory Carrier 30

As shown in FIG. 2 and FIG. 4, the injection molding section 14 of thepreform molding station 10 is provided with a lower clamping plate 20mounted on the machine bed 8. A for example circular upper clampingplate 22 is disposed above this lower mold clamping plate 20 and extendsfrom the injection molding section 14 into the preform ejecting section16. This upper mold clamping plate 22 is movable vertically along fourtie bars 24 provided in four locations around the injection moldingsection 14. As shown in FIG. 1, FIG. 2 and FIG. 4, a fixed plate 26 ismounted on the upper ends of the tie bars 24 and a clamping cylinder 28is mounted on this fixed plate 26. The clamping cylinder 28 drives aclamping rod 28a (see FIG. 4), and the upper clamping plate 22 is drivenup and down by this clamping rod 28a.

As shown in FIG. 2 to FIG. 4, the rotary disc 30 constituting the firstcirculatory carrier is rotatably mounted at the underside of the upperclamping plate 22. As shown in FIG. 7, this rotary disc 30 is fixed to arotational shaft 34 rotationally driven by a rotary actuator 32 fixed tothe upper clamping plate 22. As shown in FIG. 5, which is an undersideview of the rotary disc 30, the two injection core molds 50 and the twoneck cavity molds 60 are mounted on the rotary disc 30 in positionscorresponding to the injection molding section 14 and the preformejecting section 16. The details of the injection core molds 50 and theneck cavity molds 60 will be discussed in detail later.

As shown in FIG. 2 and FIG. 4, the injection molding section 14 isprovided with a hot runner mold 40 with which a nozzle of the injectingapparatus 12 nozzle-touches, and the injection cavity mold 42 is mountedon this hot runner mold 40. This injection cavity mold 42 has a cavityfor each of the N preforms 1 simultaneously molded in the injectionmolding section 14, for example four cavities. This injection cavitymold 42 is capable of cooling the injection molded preforms, and acoolant, for example water at room temperature, is circulatedtherethrough.

As shown in FIG. 4 to FIG. 8, the two injection core molds 50 mounted onthe rotary disc 30 each have the same number of core pins 52 as thenumber N of preforms simultaneously molded, for example four core pins52. As shown in FIG. 7, the base portions 52a of these core pins 52 aresupported by a core presser plate 54 fixed to the underside of therotary disc 30 and a core fixing plate 56 fixed to the underside of thiscore presser plate 54. When the clamping cylinder 28 is driven and theclamping rod 28a drives down the upper clamping plate 22, the core pins52 of the injection core mold 50 are driven down integrally with therotary disc 30, the core presser plate 54 and the core fixing plate 56mounted on this upper clamping plate 22 and are thereby clamped onto theinjection cavity mold 42.

As shown in FIG. 7 and FIG. 11, the two neck cavity molds 60 mounted onthe rotary disc 30 are made up of pairs of split molds 62a and 62b, eachneck cavity mold 60 comprising the same number of pairs of split molds62a and 62b as the number N of preforms simultaneously molded, forexample four. The pairs of split molds 62a and 62b of each neck cavitymold 60 are fixed by split plates 64a and 64b, and these split plates64a and 64b constitute a neck fixing plate 64. As shown in FIG. 11, aneck presser plate 65 which pushes this neck fixing plate 64 downward isdisposed on the upper surface side of the split plates 64a and 64b.Also, there are provided guide plates 66 which support the undersides ofthe ends of the neck fixing plate 64. The split plates 64a and 64b arekept normally closed by springs 64c shown in FIG. 5. As shown in FIG. 5,a wedge hole 64d is provided at each end of the split plates 64a and64b. After the neck fixing plate 64 has been carried into the preformejecting section 16, the split plates 64a and 64b are opened by beingdriven apart along the guide plates 66 by split plate opening cams 108,which will be further discussed later, driven into the wedge holes 64d.

As shown in FIG. 9, which is an enlarged sectional view of portion A ofFIG. 8, and in FIG. 6, at each end of each guide plate 66 a verticallifting and lowering pin 70 has its lower end fixed in the guide plate66, and a flange 70a is formed at the upper end of this lifting andlowering pin 70. A guide cylinder 72 extends downward from the undersideof the rotary disc 30, and the lifting and lowering pin 70 is disposedinside this guide cylinder 72. A return spring 74 is disposed betweenthe inner wall of the bottom portion of the guide cylinder 72 and theflange 70a of the lifting and lowering pin 70. The upward urging forceof these return springs 74 urges the guide plate 66 upward at all times,and as a result the neck presser plate 65 is normally in contact withthe underside of the core fixing plate 56.

By this state of contact between the core fixing plate 56 and the neckpresser plate 65 being maintained, the injection core mold 50 and theneck cavity mold 60 are kept clamped together. When in the preformejecting section 16 an external force (which will be further discussedlater) is applied to the lifting and lowering pins 70, the lifting andlowering pins 70 descend against the urging force of the return springs74 and the neck presser plate 65 is driven down so that it moves awayfrom the underside of the core fixing plate 56 and pushes the neckfixing plate 64 downward. As a result, the core pins 52 of the injectioncore mold 50 are released from the preforms 1 whose neck portions 2 areheld by the neck cavity mold 60.

Preform Ejecting Section 16

Next, the construction of the preform ejecting section 16, and inparticular the preform ejection drive mechanism will be described. Inthis preferred embodiment, the preform ejection drive mechanism is madeup of a neck mold-release driver 80 and a split mold opening driver 100.As shown in FIG. 8, the neck mold-release driver 80 has a first cylinder82, and this first cylinder 82 is mounted on a first cylinder mountingplate 84b supported on the upper clamping plate 22 by way of firstsupport rods 84a. The first cylinder 82 drives a first raising andlowering plate 86 up and down by way of a first piston rod 82a. Presserdrive rods 88 are provided at each end of this first raising andlowering plate 86. Holes 22a are provided in the upper clamping plate 22passing through from the upper surface to the lower surface thereof, andthe presser drive rods 88 are disposed in these holes 22a. The initialposition of the first raising and lowering plate 86 is a position suchthat the ends of the presser drive rods 88 do not project below theunderside of the upper clamping plate 22 so they do not obstruct therotation of the rotary disc 30.

As shown in FIG. 8, the rotary disc 30, the core presser plate 54 andthe core fixing plate 56 respectively have holes 30a, 54a and 56a inpositions facing the holes 22a in the upper clamping plate 22. Drivenrods 68 disposed in the holes 30a, 54a and 56a are mounted on the uppersurface of the neck presser plate 65.

As a result, when the first cylinder 82 is driven, the neck presserplate 65 and the neck fixing plate 64 are driven down against the urgingforce of the return springs 74 by the first cylinder 82 by way of thefirst piston rod 82a, the presser drive rods 88 and the driven rods 68.As shown in FIG. 10, this causes the core pins 52 of the injection coremold 50 to release from the preforms 1 whose neck portions 2 are held bythe neck cavity mold 60. In this preferred embodiment, the core pins 52of the injection core mold 50 do not have to be pulled completely clearof the open ends of the preforms 1, it only being necessary that atleast gaps through which air can enter form between the core pins 52 andthe inner walls of the preforms 1. In this preferred embodiment, thedownward stroke of the neck fixing plate 64, that is the releasingstroke of the core pins 52 (the length L shown in FIG. 10), is set atfor example 50 mm.

Next, the split mold opening driver 100 will be described. As shown inFIG. 1 and FIG. 8, this split mold opening driver 100 has for exampletwo second cylinders 102. These second cylinders 102, as shown in FIG.11, are mounted on a second cylinder mounting plate 104b supported onthe first raising and lowering plate 86 by way of second support rods104a. As a result, when the first raising and lowering plate 86 isdriven up or down by the first cylinder 82, the second cylinders 102 arealso moved up or down at the same time. These second cylinders 102 drivesecond raising and lowering plates 106 up and down by way of secondpiston rods 102a. The split plate opening cams 108 are mounted on thesesecond raising and lowering plates 106. The lower end portions of thesesplit plate opening cams 108 are of a wedge shape fitting the wedgeholes 64d formed in the split plates 64a and 64b constituting the neckfixing plate 64. By driving the second cylinders 102 the split plateopening cams 108 are driven down and the wedge portions at their endsare thereby inserted into the wedge holes 64d in the neck fixing plate64, and this opens the split plates 64a and 64b. Consequently the pairsof split molds 62a and 62b mounted on this pair of split plates 64a and64b are opened, and the preforms 1 are ejected from the neck cavity mold60. In this preferred embodiment the drive timing of the secondcylinders 102 is set to after the first cylinder 82 is driven.

Next, the operation of the preform molding station 10 of the apparatusof the preferred embodiment will be described.

Injection Molding in Injection Molding Section 14

The clamping cylinder 28 is driven and the upper clamping plate 22 isthereby driven down, whereby the injection core mold 50 and the neckcavity mold 60 are clamped to the injection cavity mold 42. After theclamped state shown in FIG. 4 is reached, by a screw inside theinjecting apparatus 12 being advanced and rotated, the preforms 1injection molding material, for example polyethylene terephthalate(PET), is injected by way of the hot runner mold 40 into the cavitybounded by the molds 42, 50 and 60, and the preforms 1 are therebyinjection molded.

Cooling Step in Injection Molding Section 14

The injection cavity mold 42, the injection core mold 50 and the neckcavity mold 60 each have a coolant, for example water at roomtemperature, circulating through them, and the resin injected into thecavity bounded by the molds can be immediately cooled.

Injection Cavity Mold 42 Mold-Release Step in Injection Molding Section14

By the clamping cylinder 28 being so driven that it lifts the upperclamping plate 22, the injection core mold 50 and the neck cavity mold60 can be lifted up away from the injection cavity mold 42 as shown bythe mold-open state of FIG. 10. At this time, because the neck portions2 of the preforms 1 form an undercut with respect to the mold-releasedirection, the injection molded preforms 1 are held on the injectioncore mold 50 and neck cavity mold 60 side and are released from theinjection cavity mold 42.

The timing at which this mold-release starts in the injection moldingsection 14 can be made considerably earlier than a conventionalmold-release starting timing. In other words, the cooling time of thepreforms 1 in the injection molding section 14 can be shortened. This isbecause even after the preforms 1 have been released from the injectioncavity mold 42 the core pins 52 of the injection core mold 50 remaininside the preforms 1 and deformation of the preforms 1 accompanyingtheir thermal contraction can be prevented. Therefore, the mold-releasetemperature of the preforms 1 in the injection molding section 14 onlyhas to be low enough for a skin layer thick enough for the shape of thepreforms 1 to be maintained after they are released from the injectioncavity mold 42 to form at the outer surfaces of the preforms 1, and canbe higher than conventional mold-release temperatures. Even if themold-release temperature is high like this, because the cooling causesthe preforms 1 to contract around the core pins 52 of the injection coremold 50, mold-release from the injection cavity mold 42 can be carriedout relatively smoothly, and preform 1 mold-release problems do notoccur. Also, because in the injection molding section 14 withdrawal ofthe core pins 52 is not carried out, even if the preforms 1 aremold-released at a high mold-release temperature, the mold-releaseproblem of the lower ends of the preforms 1 being lifted together withthe core pins 52 does not occur.

The clamped state of the injection core mold 50 and the neck cavity mold60 with respect to the preforms 1 released from the injection cavitymold 42 is maintained by the core fixing plate 56 and the neck presserplate 65 being kept in contact with each other by the return springs 74.This clamped state of the injection core mold 50 and the neck cavitymold 60 is maintained through the subsequent preforms 1 carrying stepand until in the preform ejecting section 16 the injection core mold 50is released from the preforms 1. Cooling of the preforms 1 is possiblethroughout the time during which this clamped state of the injectioncore mold 50 and the neck cavity mold 60 is maintained.

Preforms 1 Carrying Step

The preforms 1 are carried from the injection molding section 14 to thepreform ejecting section 16 by the rotary actuator 32 being driven andthe rotary disc 30 constituting the first circulatory carrier beingrotated thereby through 180°. During this preforms 1 carrying step, itis possible for cooling of the preforms 1 by the coolant circulatingthrough the injection core mold 50 and the neck cavity mold 60 tocontinue without interruption.

Generally, when the preforms 1 are mold-released at a high temperature,crystallization occurs due to inadequate cooling and the wall surfacesof the preforms 1 become nontransparent, and particularly when PET isbeing used to make transparent containers this is a fatal defect.According to experiments carried out by the present inventors, thiscrystallization and loss of transparency of the preforms 1 accompanyinginadequate cooling is particularly marked at the inner wall sides of thepreforms 1. This is because at the inner wall side of a preform 1 thereis less surface area in contact with the mold and consequently the innerwall is more liable to be inadequately cooled than the outer wall. Also,when as in the past the injection cavity mold 42 and the injection coremold 50 are released from the preforms 1 in the injection moldingsection, the inner wall side is more liable to be inadequately cooledthan the outer wall because the heat-radiating surface area at the innerwall side of the preform 1 is smaller than at the outer wall side andfurthermore heat is confined in the interior of the preform 1.

In this preferred embodiment, even if in the injection molding portion14 the preforms 1 are mold-released at a relatively high temperature, inthe subsequent carrying step it is possible for the preforms 1 tocontinue to be cooled by the injection core mold 50 and the neck cavitymold 60. In particular, because the inner walls of the preforms 1 can beuninterruptedly cooled by the core pins 52 of the injection core mold50, crystallization and loss of transparency caused by inadequatecooling can be certainly prevented. Also, the neck portions 2, whichbecause they are thick have large heat capacities and are more liable tocrystallize than other portions, can be cooled by the neck cavity mold60 and prevented from crystallizing.

Preform Cooling Step in Preform Ejecting Section 16

Even after the preforms 1 have been carried into the preform ejectingsection 16, by the clamped state of the injection core mold 50 and theneck cavity mold 60 with respect to the preforms 1 being maintained, thepreforms 1 can be cooled as they were during the above-mentionedcarrying step. At this time, even if in the injection molding section 14the clamping cylinder 28 has been driven and the upper clamping plate 22lowered for the injection molding of the next preforms, because theabove-mentioned clamped state in the preform ejecting section 16 ismaintained, cooling of the preforms 1 can be continued.

Separation of Neck Cavity Mold 60 from Injection Core Mold 50

Cooling of the preforms 1 by the core pins 52 of the injection core mold50 only has to continue long enough for crystallization caused byinadequate cooling of the inner walls of the preforms 1 to be preventedand for deformation of the ejected preforms 1 to be avoided, and indeedif the preforms 1 are excessively cooled by the core pins 52, removal ofthe core pins 52 becomes difficult. Therefore, in this preform ejectingsection 16, first the injection core mold 50 is released from thepreforms 1. In this preferred embodiment, this is achieved by the neckcavity mold 60 holding the preforms 1 being released from the injectioncore mold 50.

This separation of the neck cavity mold 60 is carried out by the neckpresser plate 65 kept in contact with the core fixing plate 56 by theurging force of the return springs 74 being lowered by the neckmold-release driver 80. When the first cylinder 82 of the neckmold-release driver 80 is driven, the pushing force thereof transmittedthrough the first piston rod 82a, the first raising and lowering plate86, the presser drive rods 88 and the driven rods 68 causes the neckfixing plate 64 to be pressed against the neck presser plate 65 and bedriven downward as shown in FIG. 6 and FIG. 10. At this time, becausethe preforms 1 have their neck portions 2 held by the neck cavity mold60, the preforms 1 are also driven downward together with the neckfixing plate 64 and the neck cavity mold 60. Consequently, theseparation of the neck cavity mold 60 from the injection core mold 50results in the injection core mold 50 being released from the preforms1.

This mold-releasing stroke of the injection core mold 50 with respect tothe preforms 1 does not have to be so long that the core pins 52 arepulled completely clear of the open ends of the preforms 1 for thesubsequent carrying of the preforms 1 as it does conventionally, andneed only be long enough for at least gaps through which air can enterto be formed between the inner walls of the preforms 1 and the core pins52. Consequently, the mold-releasing stroke of the injection core mold50 depends on the angle of the removal taper provided on the core pins52 and the inner walls of the preforms 1, and the greater this removaltaper angle is, the shorter the mold-release stroke need be. Because themold-releasing stroke of the injection core mold 50 can be shortened inthis way the installation height of the first cylinder 82 can be madelow and the overall height of the injection molding apparatus can bemade low, and this is advantageous in the transportation andinstallation of the apparatus.

Preforms 1 Ejection Step in Preform Ejecting Section 16

Because the preforms 1 have their neck portions 2 held by the neckcavity mold 60 comprising the pairs of split molds 62a and 62b, thepreforms 1 can be ejected by this neck cavity mold 60 being released. Tobring this about, the second cylinders 102 of the split mold openingdriver 100 are driven. This driving force of the second cylinders 102 istransmitted to the split plate opening cams 108 by way of the secondpiston rods 102a and the second raising and lowering plates 106. By thesplit plate opening cams 108 being driven downward, as shown in FIG. 11their ends are inserted into the wedge holes 64d formed in the splitplates 64a and 64b, these split plates 64a and 64b are driven open, andthe pairs of split molds 62a and 62b are thereby opened. At this time,even if a neck portion 2 of a preform 1 has stuck to one of the splitmolds 62a, 62b and tries to move therewith, because the respective corepin 52 of the injection core mold 50 is still inside the preform 1,lateral movement of the preform 1 is restricted and the preform 1 can bedropped downward without fail.

In the state before the split plate opening cams 108 are drivendownward, in order to avoid the split plate opening cams 108 interferingwith the rotation of the rotary disc 30 it is necessary that their endsstop within the thickness of the upper clamping plate 22. On the otherhand, because the neck fixing plate 64 which is driven open by thesesplit plate opening cams 108 is in the farthest position from the rotarydisc 30, the downward stroke of the split plate opening cams 108 islong. In this preferred embodiment, because the second cylinders 102which drive these split plate opening cams 108 are mounted on the firstraising and lowering plate 86 driven by the first cylinder 82 andbecause before the split plate opening cams 108 are driven the firstraising and lowering plate 86 is driven, the actual downward strokethrough which the split plate opening cams 108 are driven by the secondcylinders 102 is short. As a result, the installation height of thesecond cylinders 102 can be made low, the overall height of theinjection molding apparatus an be made low, and an apparatusadvantageous from the points of view of transportation and installationcan be provided.

After this preform 1 ejecting step is finished, the first and secondcylinders 82 and 102 return to their original states. As a result, theneck presser plate 65 is brought back into contact with the core fixingplate 56 by the return springs 74, and the injection core mold 50 andthe neck cavity mold 60 are returned to their clamped state inpreparation for the next injection molding.

The cooling and mold-releasing steps described above carried out in thepreform ejecting section 16 only have to be finished within the timetaken for the injection molding of the next, new preforms in theinjection molding section 14 to finish, in other words within theinjection molding cycle time. The preform 1 cooling time dependsparticularly on the thickness of the trunk portions of the preforms 1,and the thicker the preforms 1 are the longer the cooling time that mustbe provided. In this preferred embodiment this cooling time can beadjusted by way of the setting of the timing of the mold-release of theinjection core mold 50 in the preform ejecting section 16 as well as byadjusting the cooling time in the injection molding section 14. As aresult, even while the mold-release temperature in the injection moldingsection 14 is made high and the injection molding cycle time therebyshortened, because adjustment of the cooling time is easy a highlyflexible preform injection molding station can be provided.

After the preform 1 injection molding in the injection molding section14 is finished, the injection core molds 50 and the neck cavity molds 60in the two sections 14 and 16 are changed around by the rotary disc 30being rotated through 180° by the rotary actuator 32. In this preferredembodiment, the rotary actuator 32 consists of reversible rotarycarrying means of which the rotary carrying direction reverses eachtime. As a result, even if the injection core molds 50 and the neckcavity molds 60 rotationally carried have cooling pipes for circulatingcoolant therethrough connected thereto, these cooling pipes will not betwisted through more than one revolution. Consequently, it is possibleto connect these cooling pipes to the molds without using rotaryconnectors and their construction does not become complicated.

Because for the reasons discussed above the preforms 1 are given auniform temperature or a suitable temperature distribution, it ispossible to mold bottles of a desired thickness. Also, because whiteningcrystallization of the bottles is prevented, highly transparent bottlescan be molded. This invention is not limited to being applied to the hotparison blow molding described above, and of course can also be appliedto so-called cold parison blow molding wherein the preforms are returnedto room temperature before being heated again and blow molded. In thiscase also, there is the effect that the injection molding cycle time canbe shortened.

Transfer Station 200

Next, the constitution and operation of the transfer station 200 will bedescribed with reference to FIG. 2, FIG. 12 to FIG. 14 and FIG. 21 andFIG. 22. FIG. 12 to FIG. 15 show a mechanism corresponding not to thepreferred embodiment apparatus shown in FIG. 1 but rather correspondingto a preferred embodiment apparatus shown in FIG. 21. FIG. 21 shows acase wherein the above-mentioned numbers N and n of preforms moldedsimultaneously are respectively N=6 and n=2, and accordingly themechanisms of the transfer station 200 shown in FIG. 12 to FIG. 15transfer n=2 preforms 1 simultaneously. The case wherein n=1 preform 1is transferred at a time is exactly the same as the case where n=2except in that there is no transfer pitch conversion, which will befurther discussed later.

This transfer station 200 has a receiving and lowering mechanism 210which receives and lowers preforms 1 ejected from the preform ejectingsection 16 of the preform molding station 10, and an inverting andhanding over mechanism 230 which then turns the preforms 1 upside-downand hands them over to the preform receiving section 304 of the blowmolding station 300.

Receiving and Lowering Mechanism 210

FIG. 12 and FIG. 13 respectively show the receiving and loweringmechanism 210 in a raised position and a lowered position. Thisreceiving and lowering mechanism 210 has a bottom portion holding part214 which holds the bottom portion 3 of a preform 1 and a neck lowerportion holding part 218 which supports a support ring 2a formed at thelower end of the neck portion 2 of the preform 1. The bottom portionholding part 214 is mounted on a rod 212a of a first raising andlowering drive device 212 comprising an air cylinder or the like and ismovable up and down between the raised position in which it is shown inFIG. 12 and the lowered position in which it is shown in FIG. 13. Thisvertical stroke b is shown in FIG. 4.

The neck lower portion holding part 218 is movable up and down togetherwith the bottom portion holding part 214 and is movable horizontallythrough a horizontal stroke a shown in FIG. 4. To make this possible, afirst slider 220 is disposed on a rail 222 slidably therealong. Thisfirst slider 220 is driven horizontally by a rod 216a of a firstadvancing and withdrawing drive device 216 comprising an air cylinder orthe like. The neck lower portion holding part 218 has a small diametershaft portion 218a at its lower part and a large diameter shaft portion218b at its upper part, and the small diameter shaft portion 218a passesthrough a stopper member 220a mounted on the first slider 220. A flange218c is fixed to the lower end of the small diameter shaft portion 218awhich projects below this stopper member 220a. Also, a spring 218d isdisposed around a portion of the small diameter shaft portion 218aprojecting upward of the bottom portion holding part 214. Because thisspring 218d is disposed between the bottom portion holding part 214 andthe large diameter shaft portion 218b, the large diameter shaft portion218b is pushed upward by the spring 218d as the bottom portion holdingpart 214 ascends, and the neck lower portion holding part 218 canthereby be raised. When the first advancing and withdrawing drive device216 is driven, because this horizontal driving force is transmitted byway of the first slider 220 to the shaft portions 218a and 218b, theneck lower portion holding part 218 is caused to slide horizontally.This sliding stroke a is shown in FIG. 4.

The operation of this receiving and lowering mechanism 210 will now beexplained with reference to FIG. 4, FIG. 12 and FIG. 13. Before the neckcavity mold 60 is driven open in the preform ejecting section 16 of thepreform molding station 10, the bottom portion holding part 214 and theneck lower portion holding part 218 are disposed in the positions inwhich they are shown in FIG. 12. In this state shown in FIG. 12, theraised position of the neck lower portion holding part 218 is determinedby the flange 218c thereof abutting with the stopper member 220a. Thebottom portion holding part 214 is stopped in a position which itreaches by compressing the spring 218d after the neck lower portionholding part 218 has reached its upper limit position. At this time, theneck lower portion holding part 218 is in a position wherein it iswithdrawn to the right in FIG. 4 and FIG. 12 of a position directlybelow the support ring 2a of the preform 1. When the neck cavity mold 60is driven open, the preform 1 drops downward and its bottom portion 3 iscaught by the bottom portion holding part 214. At this time, as shown inFIG. 12, the preform 1 does not completely release from the core pin 52and the preform 1 maintains an upright state with a portion of the corepin 52 remaining inserted therein.

After that the first advancing and withdrawing drive device 216 isdriven, and the neck lower portion holding part 218 is moved to the leftthrough the stroke a (see FIG. 4). As a result, the neck lower portionholding part 218 is positioned directly below the support ring 2a of thepreform 1.

After that, the first raising and lowering drive device 212 is so driventhat it pulls in the rod 212a, and the bottom portion holding part 214starts to be lowered. In the initial stage of this lowering, until thespring 218d returns to its original length, the neck lower portionholding part 218 stays in its upper position. As a result, during theinitial stage of this lowering, the bottom portion holding part 214moves away from the bottom portion 3 of the preform 1 and the supportring 2a of the preform 1 comes to rest on the neck lower portion holdingpart 218. The first raising and lowering drive device 212 continues tobe driven after this, and the preform 1 descends with its support ring2a being held by the neck lower portion holding part 218 only. It ispreferable that members of low thermal conductivity, for examplesynthetic resin or the like, be used for the portions of the bottomportion holding part 214 and the neck lower portion holding part 218which make contact with the preform 1. The preform 1 supported by theneck lower portion holding part 218 continues to be lowered until itreaches the position in which it is shown in FIG. 13.

Inverting and Handing Over Mechanism 230

Next, the constitution of the inverting and handing over mechanism 230will be described with reference to FIG. 4 and FIG. 13 to FIG. 15. Thisinverting and handing over mechanism 230 has two neck holding mechanisms232 corresponding to the number n=2 of preforms simultaneously blowmolded in the blow molding section 310 shown in FIG. 21 (see FIG. 14).The neck holding mechanisms 232 each have an open/closeable pair of neckholding members 234 which hold the neck portion 2 of the preform 1. Asshown in FIG. 15, these two neck holding mechanisms 232 are mounted on asupport table 236, and this support table 236 is linked to a rod 238a ofa second raising and lowering drive device 238 comprising and aircylinder or the like. As a result, the two neck holding mechanisms 232are movable vertically through a vertical stroke e shown in FIG. 4. Inorder to make this vertical movement smooth, for example two guide rods240 are provided and guided by guide portions 242.

The second raising and lowering drive device 238 and the guide portions242 described above are mounted on a second slider 244 as shown in FIG.15. This second slider 244 is provided with a horizontal drive device246 which moves the second slider 244 in the direction in which thenumber of preforms N, for example 4, simultaneously molded in theinjection molding section 14 are arrayed. This horizontal drive device246 moves the second slider 244 horizontally by means of for example aball screw 246a. The horizontal drive device 246 is mounted on a thirdslider 248, and this third slider 248 is provided with a secondadvancing and withdrawing drive device 250 which advances and withdrawsthe raising and lowering drive device 238 through the advancing andwithdrawing stroke c shown in FIG. 4. That is, as shown in FIG. 14, arod 250a of the second advancing and withdrawing drive device 250 islinked to the third slider 248.

Also, there is provided an inverting drive device 252 which rotates thetwo neck holding mechanisms 232 through 180° about a horizontal axis.The 180° rotational stroke d of this inverting drive device 252 is shownin FIG. 4. As a result of this inversion the preform 1 moves from anupright state wherein the neck portion 2 faces upward to an invertedstate wherein the neck portion 2 faces downward.

Next, the operation of this inverting and handing over mechanism 230will be explained. When the preforms 1 reach their lowered positions asshown in FIG. 13, the neck holding mechanisms 232 which are in a standbyposition shown with chain lines in FIG. 13 are rotated through 180° bythe inverting drive device 252. Opening and closing drive mechanismsincorporated into the neck holding mechanisms 232 close the pairs ofneck holding members 234, and the neck portions 2 of the preforms 1 areheld by these neck holding members 234. Then the preforms 1 areinverted. Before that, however, to prevent the preforms 1 frominterfering with other members, the neck lower portion holding part 218is withdrawn to the right through the moving stroke a (see FIG. 4), andby the third slider 248 being moved to the left through the movingstroke c (see FIG. 4) the two neck holding mechanisms 232 are moved tothe left. After that, by the preforms 1 being rotated through 180° bythe inverting drive device 252, the preforms 1 reach the position shownwith chain lines in FIG. 13. Then, by the two neck holding mechanisms232 being lowered by the second raising and lowering drive device 238through the stroke e (see FIG. 4), the preforms 1 can be placed oncarrier members 330 positioned in the preform receiving section 304 ofthe blow molding station 300. After that, the neck holding mechanisms232 are opened and moved through the vertical stroke e and thetransverse stoke c shown in FIG. 4 whereby the neck holding mechanisms232 are moved away from the preforms 1 and returned to their standbyposition shown with chain lines in FIG. 13.

When the above transfer operation is carried out in the preferredembodiment apparatus shown in FIG. 21 wherein the number ofsimultaneously blow molded preforms 1 is n=2, n=2 preforms 1 aretransferred simultaneously. The transferred two preforms 1 are handedover to carrier members 330 in two receiving positions 260. At thistime, the pitch P2 at which the neck holding mechanisms 232 receive thetwo preforms 1 from the receiving and lowering mechanism 210 isdifferent from the pitch P3 at which the neck holding mechanisms 232deliver the two preforms 1 to the carrier members 330. This is becauseduring the transfer of the preforms 1 pitch conversion is performed by apitch change drive device 254; this point will be further discussedlater. In the case of the preferred embodiment apparatus of FIG. 1wherein the number of preforms 1 simultaneously blow molded is n=1, thepreform 1 is delivered to a carrier member 330 positioned between thetwo receiving positions shown in FIG. 14. Therefore, each time aninjection molding operation in which N=4 simultaneously injection moldedpreforms 1 are injection molded is finished, transfer of one preform 1at a time is repeated four times.

Blow Molding Station 300

Next, the blow molding station 300 will be described with reference to41, FIG. 4 and FIG. 16 to FIG. 20.

Second Circulatory Carrier 302 and Preform Receiving Section 304

This blow molding station 300 circulates the carrier member 330 carriedby the second circulatory carrier 302 in order through the preformreceiving section 304, the heating section 306, the standby section 308,the blow molding section 310 and the bottle ejecting section 312. Asshown in FIG. 1, the second circulatory carrier 302 has four sprockets320a to 320d, and for example only the sprocket 320a is driven and theother sprockets 320b to 320d are not driven. An endless carrier chain322 runs around these four sprockets 320a to 320d. Some other endlessdrive member, such as a belt, for example a V-belt or a toothed belt,can be used instead of the chain, and other rotary drive members such aspulleys can be used instead of the sprockets.

In the preferred embodiment apparatus shown in FIG. 1, ten carriermembers 330 are fixed to the carrier chain 322. This fixing structure isas follows:

As shown in FIG. 18, each carrier member 330 has a cylindrical mountportion 332. This mount portion 332 has is provided at one side thereofwith projecting portions 334a and 334b which respectively project aboveand below the carrier chain 322, sandwiching the carrier chain 322.Adjacent chain links in the carrier chain 322 are connected by hollowpins, and the upper and lower projecting portions 334a and 334b arelinked to the carrier chain 322 by fixing pins 336 being passed throughthe central portions of the hollow pins and having their ends secured sothat they cannot drop out.

A cylinder 342 is rotatably supported by way of a bearing 340 inside thecylindrical portion of the mount part 332. The upper portion of thiscylinder 342 functions as a carrying surface 344 on which the endsurface of the neck portion 2 of an inverted preform 1 is placed. Also,a carrying pin 346 is supported inside this cylinder 342. This carryingpin 346 has a portion thereof projecting upward of the carrying surface344 which enters the neck portion 2 of the preform 1 and can support thepreform 1 in its inverted state. Thus, the carrying surface 344 and thecarrying pin 346 constitute a preform 1 supporting portion.

As shown in FIG. 16, three cam followers 338 consisting of rollers orthe like are supported on this carrier member 330. Two of the camfollowers 338 roll along the inner side locus described when the carriermember 330 is driven by the carrier chain 322. The other cam follower338 rolls along the outer side locus. These three cam followers 338 areguided by a carrier base 324 or by rails 326, depending on where thecarrier member 330 is in the blow molding station 300. As shown in FIG.18, the two rails 326 are disposed on either side of the carrying pathand each are formed with a C-shaped cross-section and have a cam surface326a. These rails 326 have portions which so project that they cover theupper portions of the cam followers 338, and the cam followers 338cannot leave the rails 326. These rails 326 are disposed in the blowmolding section 310.

On the other hand, in all parts of the carrying path outside the blowmolding section 310, for example as shown in FIG. 19 showing the heatingsection 306, the carrier base 324 is provided below the carrying path.Upper surfaces of this carrier base 324 constitute cam surfaces 324a.Portions of the rails 326 disposed in the heating section 306 are sodisposed that they cover the upper portions of the cam followers 338 andprevent the cam followers 338 from escaping from their travel paths.Because if the carrier base 324 were provided in the blow moldingsection 310 it would not be possible for a drawing rod and a blow coremold to be inserted from below into the preform 1, such a constructionis not used.

An autorotation sprocket 348 is mounted on the cylinder 342 of thecarrier member 330. When the preform 1 is in the heating section 306,this autorotation sprocket 348 rotates the preform 1 about its verticalaxis; this point will be further discussed in the description of theheating section 306.

The driving sprocket 320a repeats an intermittent carrying movementwherein it moves by an amount corresponding to one pitch of the carriermembers 330 fixed to the carrier chain 322 at a predetermined pitch andthen stops for a predetermined period of time. By the preform 1 beingreceived in an inverted state by the preform receiving section 304 ofthe blow molding station 300 the preform 1 is placed on the carryingsurface 344 of the carrier member 330 and the carrying pin 346 isinserted into the neck portion 2 of the preform 1. When after that thedriving sprocket 320a is driven and rotates, the carrier chain 322meshing with the sprockets 320a to 320d moves and the carrier members330 are thereby moved by one pitch. By this carrying operation beingrepeated, the preforms 1 received in the preform receiving section 304are carried through the heating section 306 and the standby section 308to the blow molding section 310, and here they are drawn and blow moldedinto bottles 6. After that the bottles 6 on the carrier members 330 arecarried to the bottle ejecting section 312, and here the bottles 6 areejected to outside the apparatus.

Heating Section 306

Next, the heating section 306 will be described with reference to FIG.19 and FIG. 20.

The heating section 306 heats the preform 1 by means of radiant heat ina space enclosed by a heating box cover 350. As described above, in theapparatus of this preferred embodiment, the preform 1 can be amplycooled by the injection core mold 50 while it is being carried to thepreform ejecting section 16 and in the preform ejecting section 16 untilthe injection core mold 50 is released from the preform 1. As a result,while the method is still a hot parison method, the preform 1 can beamply cooled and can be cooled to a temperature lower than a suitableblow molding temperature. For this reason, in the apparatus of thispreferred embodiment, the preform 1 is heated in the heating section 306provided in the blow molding station 300 until it reaches a temperaturesuitable for blow molding.

Inside the heating box cover 350 of the heating section 306 there areprovided first to fourth barlike heaters 352a to 352d constituting afirst heater set disposed spaced apart in the axial direction of thepreform 1. The barlike heaters 352a to 352d are for example infraredheaters, and extend in the preform 1 carrying direction inside theheating box cover 350. The first and second barlike heaters 352a and352b are partly surrounded by a focussing reflecting plate 354a, andheat especially the bottom portion 3 of the preform 1 with radiant heat.The third and fourth barlike heaters 352c and 352d are partly surroundedby a focussing reflecting plate 354b and heat especially the vicinity ofthe trunk portion 4 of the preform 1 with radiant heat. As shown in FIG.19, a reflecting plate 356 is disposed on the other side of the carryingpath facing the barlike heaters 352a to 352d.

Also, as shown in FIG. 19, fifth and sixth barlike heaters 352e and 352fconstituting a second heater set are disposed one on either side of thepreform 1 carrying path. These barlike heaters 352e and 352f arepositioned at such a vertical height that they face the vicinity of theneck portion 2 of the preform 1 which is draw orientated in the blowmolding section 310. The region of the preform 1 heated by these fifthand sixth barlike heaters 352e and 352f is the region which isimmediately below the neck portion 2 when the preform 1 is upright, andwill hereinafter be called the region below the neck 4a.

This region below the neck 4a is the region corresponding to theshoulder portion of the blow molded bottle 6. Consequently, when thepreform 1 is positioned inside the blow mold 378, this region below theneck 4a is in the position closest to the surface of the blow cavity.Because of this, because the transverse axis orientation rate is low,the region below the neck 4a tends to become thick, but by amply heatingthe region below the neck 4a it is possible for it to be molded to thedesired thinness. To this end, in this preferred embodiment, as well asthe fifth and sixth barlike heaters 352e and 352f being disposed inpositions where they face the region below the neck 4a of the preform 1,the heat-radiating surfaces of these heaters are disposed closer to theregion below the neck 4a than the other heaters are to the preform 1.

As shown in FIG. 20, two sprockets 360a and 360b are disposed inside theheating box cover 350 of this heating section 306, and an autorotationdrive chain 358 runs around these two sprockets 360a and 360b. Thisautorotation drive chain 358 also meshes with the autorotation sprocket348 on the carrier member 330 that has been carried into the heatingsection 306. As a result of this arrangement, when the autorotationdrive chain 358 is driven, the autorotation sprocket 348 rotates, thisrotation is transmitted by way of the cylinder 342 to the preform 1, andthe preform 1 is rotated.

As a result, when the preform 1 is carried into the heating section 306,the bottom portion 3 and the trunk portion 4 of the preform 1 receiveradiant heat both from the barlike heaters 352a to 352d disposed on oneside of the carrying path and from the reflecting plate 356 disposed onthe other side of the carrying path, and because the preform 1 isrotated it receives heat substantially uniformly in the circumferentialdirection and therefore is heated uniformly in the circumferentialdirection. Also, the region below the neck 4a of the preform 1 is amplyheated by the fifth and sixth barlike heaters 352e and 352f disposedclose to the preform 1 on either side of the carrying path, andfurthermore the rotation of the preform 1 ensures that this region belowthe neck 4a also is heated substantially uniformly in thecircumferential direction.

Here, as shown in FIG. 20, when the preform 1 carrying direction isdirection A, the direction of travel of the autorotation drive chain 358where it meshes with the autorotation sprocket 348 of the carrier member330 is made direction B, the opposite direction to direction A. Thereason for this is as follows:

If the carrier chain 322 and the autorotation drive chain 358 were bothto move at the same speed and in the same direction, direction A, therewould be no relative movement between the autorotation sprocket 348 onthe carrier member 330 side and the autorotation drive chain 358, andthe preform 1 would not rotate at all. Even if the running speeds of thecarrier chain 322 and the autorotation drive chain 358 were to bechanged, depending on the sizes of the speeds the rotation of thepreform 1 would either be extremely slow or would be reverse rotation.These situations will not occur if the autorotation drive chain 358 isdriven at a higher speed than the carrier chain 322, but normally it isnot desirable to rotate it at high speed in this way for reasonsrelating to moment. When rotated at high speed, if the preform 1 isslightly bent, this bend will be made greater by the strong moment itundergoes and this will cause uneven heating of the preform 1 andadversely affect the thickness distribution of the bottle 6.

Therefore, in the preferred embodiment shown in FIG. 20, by having thecarrier chain 322 and the autorotation drive chain 358 run in oppositedirections, when the preform I is carried in direction A the directionof its autorotation will always be the arrow C direction, and theproblems described above are eliminated. The preform 1 rotates fasterwhile it is being moved than when it is at a preform 1 stoppingposition.

Also, in this preferred embodiment, the total number of revolutionsthrough which the preform 1 is rotated while it is inside the heatingzone inside the heating box cover 350 is made a substantially integralnumber. In this preferred embodiment, `while the preform 1 is in theheating zone` refers to the time that the preform 1 spends movingthrough the distances L1, L2 and L3 (L1+L2+L3=the heating zone lengthL), as shown in FIG. 20, and the time the preform 1 spends stopped atthe two positions shown in FIG. 20. L1 is the distance over which thepreform 1 is carried between entering the heating zone and the firststopping position; L2 is the distance between the two stoppingpositions; and L3 is the distance over which the preform 1 is carriedbetween the second stopping position and leaving the heating zone. Inthis preferred embodiment, by making the number of turns through whichthe preform 1 autorotates in this carrying time and stopped time asubstantially integral number of turns, the radiant heat from both sidesof the preform 1 carrying path can be received substantially uniformlyin the circumferential direction of the preform 1 and temperaturevariation in the circumferential direction of the preform 1 can therebybe prevented.

Also, according to this preferred embodiment, the operation of heatingthe preform 1 in this heating section 306 can be carried out after anytemperature difference between the inner wall and the outer wall of thepreform 1 has been sufficiently reduced. That is, in this preferredembodiment, the preform 1 is amply cooled from the inner wall sidethereof by the injection core mold 50 in the preform molding station 10.As a result, the inner wall temperature of the preform 1 ejected in thepreform ejecting section 16 is low, and the outer wall temperature ishigh. However, this preform 1 does not immediately enter the heatingsection after a short carrying period as in the case of a so-called hotparison or 1-stage apparatus but rather enters the heating section 306after being transferred by the transfer station 200 and carried stepwiseby the carrier member 330. As a result, after the preform 1 is releasedfrom the injection molds, a considerably longer cooling time elapsesthan in a so-called 1-stage apparatus before the preform 1 enters theheating section 306. Because of this, the difference between thetemperatures of the inner and outer walls of the preform 1 can be amplymoderated. This lack of temperature difference between the inner andouter walls is the same as in so-called cold parison or 2-stageapparatuses, but because unlike the case in these apparatuses the bottle6 in this preferred embodiment can be blow molded from a preform 1 stillcontaining heat from when it was injection molded, the preferredembodiment is superior in that less heat energy has to be given to thepreforms and therefore energy can be saved.

Furthermore, with this preferred embodiment, by heating control ofpreforms 1 cooled to a temperature lower than a blow molding temperature(but considerably higher than room temperature), the stability of thepreform temperature from molding cycle to molding cycle is improved andit is possible to reduce the variation in temperature occurring when aplurality of simultaneously injection molded preforms 1 are blow moldednon-simultaneously. Also, in the apparatus of this preferred embodiment,the carrying pitch at which the preforms 1 are carried by the secondcirculatory carrier 302 is maintained at a fixed pitch. In contrast tothis, in conventional cold parison or 2-stage molding machines, thecarrying pitch is made smaller when the preforms are heated in theheating section and the carrying pitch is made larger when they enterthe blow molding section. The reason why the carrying pitch is madesmaller in the heating section is that because it is necessary to heatthe preforms all the way from room temperature to the blow moldingtemperature the total number of preforms inside the heating section ismade as large as possible in order to keep the apparatus as small aspossible. The reason why the carrying pitch is made larger in the blowmolding section, on the other hand, is that when a plurality of preformsare to be blow molded simultaneously the distance between the preformshas to be made at least greater than the maximum width of the moldedproduct. Also, preforms about to be carried into the blow moldingsection and preforms having just been carried out of the blow moldingsection have to standby outside the blow mold clamping apparatus of theblow molding section. Because of this, in conventional 1-stage moldingmachines the carrying pitch has to be changed midway around the carryingpath and the apparatus consequently is complex.

In contrast with this, in this preferred embodiment apparatus, becausebottles 6 are blow molded from preforms 1 which still contain heat fromwhen they were injection molded in the injection molding section 14, theamount of heat energy which has to be given to the preforms 1 in theheating section 306 is very small compared to a 2-stage case. As aresult, the preforms 1 can be fully reheated to the blow moldingtemperature without the total number of preforms 1 in the heatingsection 306 being increased, and it is not necessary for the carryingpitch to be changed midway around the carrying path.

Standby Section 308

As shown in FIG. 1, in the carrying path between the heating section 306and the blow molding section 310, one stop of the preform 1 performed bythe normal carrying sequence carrying out intermittent drive isallocated to the standby section 308. The provision of this standbysection 308 makes it possible to moderate the temperature distributionin the preform 1, which, being made of a synthetic resin, has poorthermal conductivity. Like the heating in the heating section 306 inthis preferred embodiment apparatus, the heating of the preform 1 isnormally carried out from the outside using radiant heat. Because ofthis, the temperature of the inner wall of the preform 1 becomes lowerthan the temperature of the outer wall. In the apparatus of thispreferred embodiment, after the preform 1 is carried out of the heatingsection 306, by stopping the preform 1 at least once in the standbysection 308 before it is carried into the blow molding section 310 it ispossible to reduce this temperature difference between the inner andouter walls and the blow molding characteristics of the bottle 6 canthereby be stabilized.

During this temperature distribution moderation in the standby section308 it is also possible to perform temperature adjustment of the preform1 actively. By actively performing temperature adjustment of the preform1 in the standby section 308 it is possible to obtain a temperaturedistribution which cannot be obtained just by heating the preform 1while rotating it in the heating section 306.

As a temperature adjusting member disposed in the standby section 308,for example a temperature adjusting core 400 which is inserted frombelow the preform 1 into the preform 1 and performs temperatureadjustment from the inner wall side over a temperature adjustment regionS can be used, as shown in FIG. 23. This temperature adjusting core 400has a first temperature adjusting core 402 which performs temperatureadjustment of the region below the neck 4a of the preform 1 from theinner wall side thereof. This temperature adjusting core 400 also has asecond temperature adjusting core 404 which performs temperatureadjustment on the trunk portion excluding the region below the neck 4a.As described above, because it is necessary to adjust the temperature ofthe region below the neck 4a to a higher temperature than other regions,in FIG. 23 the first temperature adjusting core 402 has a largerdiameter than the second temperature adjusting core 404. Alternatively,a layer consisting of a material which radiates heat of such awavelength that it is easily absorbed by the resin material from whichthe preforms 1 are molded (for example PET) may be coated onto the firsttemperature adjusting core 402.

As shown in FIG. 24, the temperature adjusting member can also be made atemperature adjusting pot 410 having a cylindrical portion which can bepositioned around the preform 1. In this case, the temperature adjustingpot 410 has blocks 414a to 414d divided into zones in the axialdirection of the preform 1 by thermal insulation 412, and each of theblocks 414a to 414d has an independent temperature adjusting fluidpassage 416 whereby independent temperature control of each zone iscarried out. Because the temperature adjusting pot 410 can be sopositioned that is covers the preform 1, a temperature distributionstepped in the axial direction of the preform 1 can be certainlyobtained. By this means, it is possible to for example adjust the regionbelow the neck 4a to a high temperature and adjust the bottom portion 3to a low temperature. As shown in FIG. 14, it is also possible to applyan internal pressure to the preform 1 by introducing air into thepreform 1 in the direction of the arrow 420 and thereby bring the outerwall of the preform 1 and the blocks 414a to 414d into contact andfacilitate the temperature adjustment.

Also, as this kind of temperature adjusting member, it is possible touse a member which in one or a plurality of locations in thecircumferential direction of the preform 1 extend in the axial directionof the preform 1 and impart the preform 1 with a temperaturedistribution in the circumferential direction thereof. For example, asshown in FIG. 25, it is possible for example at both sides of thepreform 1 to dispose a pair of cooling members 430 along the axialdirection of the preform 1 and bring them into contact with the sidewall of the trunk portion of the preform 1 using air cylinders 432 orthe like. When this is done, the preform 1 is given a temperaturedistribution in the circumferential direction, and for example as shownin FIG. 26 it is possible to fully secure the wall thickness required ofthe high transverse axis drawing rate region of a flat bottle 6. Thiskind of measure can be applied not only to flat containers but also tofor example square containers. When a temperature distribution in thecircumferential direction of the preform 1 is to be imparted, besidesbringing a cooling member into contact with the preform 1 it is alsopossible to position a heating member in the vicinity of the preform 1.

Blow Molding Section 310

The blow molding section 310 has two blow mounting plates 370 mounted onthe machine bed 8, one on either side of the preform 1 carrying path. Asshown in FIG. 4, for example four tie bars 372 are mounted crossingbetween these two blow mounting plates 370. Two blow mold clampingplates 374 which move horizontally along the four tie bars 372 aremounted between the blow mounting plates 370. These two blow moldclamping plates 374 are opened and closed symmetrically about a verticalline by a blow mold clamping mechanism 376, comprising for examplehydraulic pistons, mounted on the blow mounting plates 370.

A pair of split molds 378a and 378b constituting the blow mold 378 aremounted on these two blow mold clamping plates 374. In the case of thepreferred embodiment apparatus shown in FIG. 1, because the number n ofbottles simultaneously blow molded is n=1, a cavity for one bottle isformed in the pair of split molds 378a and 378b. In the case of thepreferred embodiment apparatus shown in FIG. 21, because the number n ofbottles simultaneously blow molded is n=2, cavities for two bottles areformed in the pair of split molds 378a and 378b.

A cylinder mounting plate 380 is mounted at a position midway along theupper two tie bars 372, and a bottom mold driving cylinder 382 ismounted on this cylinder mounting plate 380. This bottom mold drivingcylinder 382 raises and lowers a bottom mold 384. In this preferredembodiment, because the bottle 6 is blow molded from a preform 1 whichis inverted, the bottom mold 384 is made movable up and down above thepreform 1.

Thus in this preferred embodiment, while raising productivity byinjection molding N=4 preforms 1 simultaneously in the injection moldingsection 14 of the preform molding station 10, by only molding n=1 bottle6 at a time in the blow molding section 310 it is possible to raise 10the operation rate of the blow cavity mold 378. Also, by reducing thenumber of cavities in the blow cavity mold 378, which is a relativelyexpensive type of mold, mold costs, molds being consumable items, can bereduced. Furthermore, in this preferred embodiment apparatus, because inthe preform molding station 10 the preforms 1 are amply cooled beforethey are released from the injection molds, and because enough coolingtime is provided thereafter for the temperature difference between theinner and outer walls of the preforms 1 to be moderated before thepreforms 1 are heated to the blowing temperature, the uniformity of thetemperature distribution of the retained heat in the preforms 1 can beincreased and the stability of the blow molding can be greatly improved.

Bottle Ejecting Section 312

As shown in FIG. 1 and FIG. 4, the bottle ejecting section 312 isdisposed in the carrying path of the carrier members 330 carried by thesecond circulatory carrier 302 between the blow molding section 310 andthe preform receiving section 304. This bottle ejecting section 312 hasa neck holding mechanism 390 having for example a similar constructionto that of the neck holding mechanisms 232 employed in the inverting andhanding over mechanism 230. This neck holding mechanism 390 holds theneck portion of the inverted bottle 6 by means of a pair of holdingmembers. As shown in FIG. 3 and FIG. 4, there are also provided araising and lowering drive device 392 which raises and lowers this neckholding mechanism 390 and an inverting drive device 394 which invertsthe neck holding mechanism through an angle of 180°. By the neck holdingmechanism 390 being raised by the raising and lowering drive device 392,the neck portion of the bottle 6 is pulled upward off the carrying pin346 of the carrier member 330. After that, by this holding mechanism 390being rotated through 180° by the inverting device 394, the bottle 6 isbrought into an upright state to one side of the machine bed 8, and bythe pair of holding members of the neck holding mechanism then beingopened, the bottle 6 is discharged to outside the apparatus.

When Simultaneous Molding Numbers Are N=6, n=2

FIG. 21 is a plan view of a preferred embodiment apparatus wherein thesimultaneous molding numbers are N=6, n=2. The preferred embodimentshown in FIG. 21 differs from the preferred embodiment apparatus shownin FIG. 1 in the following points:

First, because the blow molding section 310 is to simultaneously blowmold two bottles 6 at a time from among the N=2 simultaneously injectionmolded preforms, the blow cavity mold 378 has two blow cavities spacedan array pitch P3 apart. The array pitch at which the carrier members330 carried by the second circulatory carrier 302 are spaced apart isthe same pitch as the array pitch P3 of the blow cavities in the blowmolding section 310. Also, the total number of carrier members fitted tothe carrier chain 322 constituting the second circulatory carrier 302 istwenty, twice as many as in the case of the preferred embodiment shownin FIG. 1. Enough preforms 1 for two blow molding cycles, 2×n=4 preforms1, are stopped inside the heating section 306. In the standby section308, enough preforms 1 for one blow molding cycle, n=2 preforms 1, aremade to standby. The carrier chain 322 and the carrier members 330 usedin the preferred embodiment apparatus of FIG. 21 are the same as thoseused in the preferred embodiment apparatus shown in FIG. 1, and it isonly the positions and pitch at which the carrier members 330 are fittedto the carrier chain 322 that are different.

In the preferred embodiment apparatus shown in FIG. 21, in the transferstation 200, the number n=2 of preforms 1 simultaneously blow molded inthe blow molding section 310 are simultaneously transferred. For this, atransfer pitch converting operation, which will now be explained withreference to FIG. 22, is necessary. In FIG. 22, six preforms 1simultaneously injection molded in the injection molding section 14 ofthe preform molding station 10 are shown as preform la to preform if. InFIG. 22, the first row on the right shows the array pitch of thepreforms 1 injection molded in the preform molding station 10. The arraypitch of the preforms 1 at this time is the same as the array pitch P1of the core pins 52 of the injection molding section 14. The second rowfrom the right in FIG. 22 shows the state of the preforms 1 before theyare received by the inverting and handing over mechanism 230 of thetransfer station 200. The array pitch of the preforms 1 here is also thepitch P1. The third row from the right in FIG. 22 shows the state of twopreforms 1 received by the preform receiving section 304 of the blowmolding station 300. The transfer of these two preforms 1 is carried outusing the two pairs of neck holding members 234 shown in FIG. 4. Thearray pitch of the preforms 1 received by the preform receiving section304 is the same as their array pitch P3 in the blow molding section 310.

Here, in the transfer station 200, when the two preforms 1 aretransferred by the two pairs of neck holding members 234, first, forexample the first and fourth preforms 1a and 1d are held. That is, thetwo preforms 1a and 1d are held and the two preforms 1b and 1c areignored this time. As a result, the array pitch P2 of the neck holdingmembers 234 at this time is P2=3×P1. This pitch conversion from thepitch P2 to the pitch P3 is carried out by the array pitch of the twoneck holding mechanisms 232 being converted by the pitch change drivedevice 254 shown in FIG. 14. Similarly thereafter, by the second andfifth preforms 1b and 1e being transferred and then the third and sixthpreforms 1c and 1f being simultaneously transferred after that, theoperation of transferring of the six simultaneously molded preforms 1 iscompleted.

When the simultaneous molding numbers N, n are made N=4, n=2, thetransfer operation in the transfer station 200 is carried out with pitchconversion from the pitch P2=2×P1 to the pitch P3 being performed andtwo preforms being held while the one preform between them is ignoreduntil the next time.

In the case of the preferred embodiment apparatus shown in FIG. 21, theratio (N/n) of the simultaneous molding numbers N and n is 3. Accordingto studies carried out by the present inventors, in the case ofgeneral-purpose medium-sized containers of capacity about 1 to 3 litershaving relatively small mouths (the diameter of the opening of the neckportion 2 being about 28 to 38 mm), the ratio of the simultaneousmolding numbers N, n should ideally be set to N:n=3:1. The reason forthis is as follows: The size of a preform for molding a general-purposemedium-sized container, although some elements do vary according to theapplication, is within a substantially fixed range. This is because thepreform size is determined by the drawing factor necessary to obtain thedrawing characteristics of polyethylene terephthalate (PET) resin andthe drawing factor necessary for molding stability. Although there issome variation depending on the use for which the container is intended,research carried out by the present inventors has shown that the maximumthickness of the trunk portion 4 of a preform 1 used for ageneral-purpose medium-sized container lies within the range 3.0 to 4.0mm.

Generally, the blow molding cycle time (the time required between when apreform 1 is carried into the blow molding section 310 and when the nextpreform 1 is carried in) required for blow molding by a blow moldingmachine is approximately 3.6 to 4.0 seconds.

In the case of this preferred embodiment, wherein the preforms 1 arecooled by the injection core mold 50 even after being released from theinjection cavity mold 42 and then blow molded thereafter, the timerequired for molding a preform for this kind of general-purposemedium-sized container is shortened to about 3/4 of that of aconventional injecting stretch blow molding machine, and an injectionmolding cycle time of approximately 10 to 15 seconds is sufficient.

Therefore, if this injection molding cycle time (approx. 10 to 15seconds) is T1 and the blow molding cycle time (3.6 to 4.0 seconds) isT2, the ratio T1:T2 is about 3:1, and it is established that in order toefficiently mold general-purpose medium-sized containers thesimultaneous molding numbers N and n should ideally be set in accordancewith this ratio. When a large container is to be molded from a thickerpreform an injection molding cycle time of 16 seconds or more issuitable and the ratio N:n can be set to around 4:1. When a smallcontainer is to be molded from a thin preform the injection moldingcycle time is shortened and consequently the ratio N:n can be set to forexample 4:2.

Thus, if N/n is set to 3, the injection molding cycle and the blowmolding cycle will be suitable for molding medium-sized containers, forwhich the market demand is the greatest, and a blow molding machine withlittle waste in the molding cycles can be realized.

Intermediate Preform Discharge Mechanism

In this preferred embodiment, as shown in FIG. 2 and FIG. 3, a preformdropout opening is provided in the part of the machine bed 8 where thetransfer station 200 is disposed. This preform dropout opening 8a iscontinuous with a chute 8b formed inside the machine bed 8, and thischute 8b leads to a preform discharge opening 8c formed in the side ofthe machine bed 8.

With this type of hot parison blow molding machine there are varioussituations wherein it is desirable that the transfer to the blow moldingstation 300 of the preforms 1 being molded in the preform moldingstation 10 be stopped. For example, when the whole blow molding machineis started up, until the preform 1 injection molding characteristicsstabilize it is preferable that the imperfect preforms 1 being producedat this stage not be supplied to the blow molding station 300. Also,when for some reason trouble has arisen in the blow molding station 300it is preferable that only the operation of the blow molding station 300be stopped and that the operation of the preform molding station 10 notbe stopped so that preforms 1 continue to be molded. This is becausethere are various heating parts in the preform molding station 10 andconsequently once the preform molding station 10 is shut down aconsiderable amount of time is required to start it up again.

In this preferred embodiment, when such a situation arises, the preforms1 continuing to be injection molded in the preform molding station 10are discharged to the side of the machine bed 8 through theabove-mentioned preform dropout opening 8a, the chute 8b and thedischarge opening 8c instead of being transferred to the blow moldingstation 300 by the transfer station 200. This preform 1 dischargingoperation can for example be carried out by the pair of neck holdingmembers 234 of the inverting and handing over mechanism 230 taking holdof the preforms 1 as usual but then, without inverting them through180°, moving the preforms 1 for example horizontally to a predeterminedposition above the preform dropout opening 8a in the machine bed 8 andthen simply releasing the preforms 1.

This preferred embodiment, as sequence control modes, has a bottlemolding operating mode wherein the preforms 1 are transferred to theblow molding station 300 and blow molding of the bottles 6 is performed,and a preform molding operating mode wherein the preforms 1 are nottransferred to the blow molding station 300. It is possible to changeover from the normal bottle molding operating mold for exampleautomatically when an abnormality is detected by a sensor or the like orby an operator flicking a manual switch. When the apparatus is switchedover to the preform molding operating mode the operation of the transferstation 200 changes over to the operation of carrying the preforms 1 tothe preform dropout opening 8a as described above, and no furtherpreforms 1 are transferred to the blow molding station 300.

This invention is not limited to the preferred embodiment describedabove, and various modifications can be made within the scope of theinvention.

In the preferred embodiment described above, the rotary disc 30 carriedboth the injection core mold 50 and the neck cavity mold 60, but forexample in cases such as when the shape of the neck portion 2 does notform an undercut with respect to the mold-release direction it is notalways necessary to use the neck cavity mold 60. When the neck cavitymold 60 is not used, after the preforms 1 are released from theinjection cavity mold 42 in the injection molding section 14, thepreforms 1 can be carried to the preform ejecting section 16 by theinjection core mold 50 alone. Because the preforms 1 contract around thecore pins 52 of the injection core mold 50 as they cool they can besmoothly released from the injection cavity mold 42, and the preform 1can be carried by the injection core mold 50 even without there beingany undercut at the neck portion 2.

In the preform ejecting section 16, to remove the injection core mold 50from the preforms 1, for example the core pins 52 of the injection coremold 50 can be provided with a function enabling them to introduce airfor ejection into the preforms 1. When this is done, in the preformejecting section 16, by blowing air from the core pins 52 into thepreforms 1 after they are cooled by the injection core mold 50, thepreforms 1 can be caused to drop downward by this air pressure.

What is claimed is:
 1. An injection stretch blow molding method whereinat least one injection blow molded preform is transferred from a preformmolding station to a blow molding station by way of a transfer stationand the at least one preform is blow molded into at least one containerin the blow molding station, the method comprising the steps of:in thepreform molding station, injection molding the at least one preform inan upright state with an open neck portion thereof facing upward; in thetransfer station, turning the at least one upright preform upside-down,bringing the at least one preform to an intermediate temperature whichis lower than a suitable blow molding temperature and is higher thanroom temperature, and transferring it to the blow molding station in aninverted state; subsequently heating the at least one inverted preformfrom about said intermediate temperature up to the suitable blow moldingtemperature; and in the blow molding station, blow molding at least onecontainer from the at least one inverted preform.
 2. The injectionstretch blow molding method according to claim 1, wherein:in the step ofinjection molding, injection molding the at least one preform using atleast an injection core mold and an injection cavity mold; and whereinthe method further comprises the steps of: releasing the at least onepreform from the injection cavity mold with the at least one preformheld by the injection core mold; carrying the injection core mold to anejecting station along a carrying path while the at least one preform iscooled by the injection core mold; and in the ejecting station, ejectingthe at least one preform by releasing it from the injection core mold.3. The injection stretch blow molding method according to claim 2,further comprising the step of:between the release of the preforms fromthe injection core mold and the start of the blow molding step, allowingthe at least one preform to cool for a period of time sufficient for atemperature difference between inner and outer walls of the at least onepreform to be moderated.
 4. The injection stretch blow molding methodaccording to claim 1, wherein:the step of injection molding comprisesinjection molding a number N (N≧2) of the preforms, using at least aninjection core mold and an injection cavity mold; and the method furthercomprises the steps of: releasing the preforms held by the injectioncavity mold; carrying the injection core mold to an ejecting stationalong a first circulatory carrying path while the preforms are cooled bythe injection core mold; in the ejecting station, ejecting the preformsby releasing the injection core mold; transferring the ejected preformsto carrier members to be carried along a second circulatory carryingpath; carrying the carrier members supporting the preforms along thesecond carrying path to the blow molding station; and wherein in theblow molding station, the step of blow molding comprises simultaneouslyblow molding n (1≦n<N) of containers from n of the preforms in a blowmold clamped around n of the preforms.
 5. The injection stretch blowmolding method according to claim 4, further comprising the stepof:between the release of the preforms from the injection core mold andthe start of the blow molding step, allowing the preforms to cool for aperiod of time sufficient for a temperature difference between inner andouter walls of the preforms to be moderated.
 6. The injection stretchblow molding method according to claim 4, wherein:the step of ejectingthe preforms is carried out after the preforms are cooled by theinjection core mold to a temperature lower than a temperature which issuitable for blow molding; and in the step of heating the preforms, thepreforms are heated in a heating station on the second carrying pathalong which preforms are carried to the blow molding station.
 7. Theinjection stretch blow molding method according to claim 6, wherein:inthe step of heating the preforms the preforms are rotated about theirvertical center axes.
 8. The injection stretch blow molding methodaccording to claim 4, wherein:in the blow molding step, a number n (n≧2)of the containers are simultaneously blow molded from n of the preformsusing n of blow cavities arrayed at a blow molding pitch P; in the stepof carrying the preforms along the second carrying path the preforms arecarried with the array pitch of the carrier members being kept equal tothe pitch P; and the step of transferring the preforms is carried out bya process of simultaneously transferring n of the preforms to n of thecarrier members being repeated a plurality of times.
 9. The injectionstretch blow molding method according to claim 8, wherein:in the step ofinjection molding the preforms, the number N of the preforms areinjection molded from polyethylene terephthalate; and wherein the ratioof the numbers N and n is N:n which equals 3:1.
 10. The injectionstretch blow molding method according to claim 9, wherein:in the step ofinjection molding the preforms, the preforms are molded with a maximumwall thickness of a barrel portion of 3.00 mm to 4.00 mm.
 11. Theinjection stretch blow molding method according to claim 4, wherein aratio N/n is an integer.
 12. The injection stretch blow molding methodaccording to claim 1, further comprising the step of:in the blow moldingstation, holding the at least one preform at a standby station after theheating step and before the blow molding step for a period of time. 13.The injection stretch blow molding method according to claim 1, whereinthe step of heating is performed using radiant heat and the heatingstation is covered.
 14. The injection stretch blow molding method ofclaim 1, wherein in the step of injection molding, the at least onepreform has a temperature greater than the suitable blow moldingtemperature, and in the step of bringing the at least one preform to atemperature which is lower than a suitable blow molding temperature, thetemperature to which the preform is brought is substantially higher thanroom temperature.